Combined warfarin-aspirin therapy: what is the evidence for benefit and harm and which patients should (and should not) receive it?

Assessment of an Intervention to Reduce Aspirin Prescribing for Patients Receiving Warfarin for Anticoagulation

IMPORTANCE

For some patients receiving warfarin, adding aspirin (acetylsalicylic acid) increases bleeding risk with unclear treatment benefit. Reducing excess aspirin use could be associated with improved clinical outcomes.

OBJECTIVE

To assess changes in aspirin use, bleeding, and thrombosis event rates among patients treated with warfarin.

DESIGN, SETTING, AND PARTICIPANTS

This pre-post observational quality improvement study was conducted from January 1, 2010, to December 31, 2019, at a 6-center quality improvement collaborative in Michigan among 6738 adults taking warfarin for atrial fibrillation and/or venous thromboembolism without an apparent indication for concomitant aspirin. Statistical analysis was conducted from November 26, 2020, to June 14, 2021.

INTERVENTION

Primary care professionals for patients taking aspirin were asked whether an ongoing combination aspirin and warfarin treatment was indicated. If not, then aspirin was discontinued with the approval of the managing clinician.

MAIN OUTCOMES AND MEASURES

Outcomes were assessed before and after intervention for the primary analysis and before and after 24 months before the intervention (when rates of aspirin use first began to decrease) for the secondary analysis. Outcomes included the rate of aspirin use, bleeding, and thrombotic outcomes. An interrupted time series analysis assessed cumulative monthly event rates over time.

RESULTS

A total of 6738 patients treated with warfarin (3160 men [46.9%]; mean [SD] age, 62.8 [16.2] years) were followed up for a median of 6.7 months (IQR, 3.2-19.3 months). Aspirin use decreased slightly from a baseline mean use of 29.4% (95% CI, 28.9%-29.9%) to 27.1% (95% CI, 26.1%-28.0%) during the 24 months before the intervention (P < .001 for slope before and after 24 months before the intervention) with an accelerated decrease after the intervention (mean aspirin use, 15.7%; 95% CI, 14.8%-16.8%; P = .001 for slope before and after intervention). In the primary analysis, the intervention was associated with a significant decrease in major bleeding events per month (preintervention, 0.31%; 95% CI, 0.27%-0.34%; postintervention, 0.21%; 95% CI, 0.14%-0.28%; P = .03 for difference in slope before and after intervention). No change was observed in mean percentage of patients having a thrombotic event from before to after the intervention (0.21% vs 0.24%; P = .34 for difference in slope). In the secondary analysis, reducing aspirin use (starting 24 months before the intervention) was associated with decreases in mean percentage of patients having any bleeding event (2.3% vs 1.5%; P = .02 for change in slope before and after 24 months before the intervention), mean percentage of patients having a major bleeding event (0.31% vs 0.25%; P = .001 for change in slope before and after 24 months before the intervention), and mean percentage of patients with an emergency department visit for bleeding (0.99% vs 0.67%; P = .04 for change in slope before and after 24 months before the intervention), with no change in mean percentage of patients with a thrombotic event (0.20% vs 0.23%; P = .36 for change in slope before and after 24 months before the intervention).

CONCLUSIONS AND RELEVANCE

This quality improvement intervention was associated with an acceleration of a preexisting decrease in aspirin use among patients taking warfarin for atrial fibrillation and/or venous thromboembolism without a clear indication for aspirin therapy. Reductions in aspirin use were associated with reduced bleeding. This study suggests that an anticoagulation clinic-based aspirin deimplementation intervention can improve guideline-concordant aspirin use.

High-risk prescribing in an Irish primary care population: trends and variation

AIMS

The aims of the present study were to examine the prevalence of high-risk prescribing (HRP) in community-dwelling adults in Ireland from 2011-2015 using consensus-validated indicators, factors associated with HRP, and the variation in HRP between general practitioners (GPs) and in the dispensing of high-risk prescriptions between pharmacies.

METHODS

A repeated cross-sectional national pharmacy claims database study was conducted. Prescribing indicators were based on those developed in formal consensus studies and applicable to pharmacy claims data. Multilevel logistic regression was used to examine factors associated with HRP and dispensing.

RESULTS

There were significant reductions in the rates of most indicators over time (P < 0.001). A total of 66 022 of 300 906 patients at risk in 2011 [21.9%, 95% confidence interval (CI) 21.8, 22.1%], and 42 109 of 278 469 in 2015 (15.1%, 95% CI 15.0, 15.3%), received ≥1 high-risk prescription (P < 0.001). In 2015, indicators with the highest rates of HRP were prescription of a nonsteroidal anti-inflammatory drug (NSAID) without gastroprotection in those ≥75 years (37.2% of those on NSAIDs), coprescription of warfarin and an antiplatelet agent or high-risk antibiotic (19.5% and 16.2% of those on warfarin, respectively) and prescription of digoxin ≥250 μg day^-1 in those ≥65 years (14.0% of those on digoxin). Any HRP increased significantly with age and number of chronic medications (P < 0.001). a) After controlling for patient variables, the variation in the rate of HRP between GPs was significant (P < 0.05); and b) after controlling for patient variables and the prescribing GP, the variation in the rate of dispensing of high-risk prescriptions between pharmacies was significant (P < 0.05).

CONCLUSIONS

HRP in Ireland has declined over time, although some indicators persist. The variation between GPs and pharmacies suggests the potential for improvement in safe medicines use in community care, particularly in vulnerable older populations.

Risk scores and geriatric profile: can they really help us in anticoagulation decision making among older patients suffering from atrial fibrillation?

OBJECTIVES

Anticoagulation for the prevention of cardio-embolism is most frequently indicated but largely underused in frail older patients with atrial fibrillation (AF). This study aimed at identifying characteristics associated with anticoagulation underuse.

METHODS

A cross-sectional study of consecutive geriatric patients aged ≥75 years, with AF and clear anticoagulation indication (CHADS₂ [Congestive heart failure, Hypertension, Age >75, Diabetes mellitus, and prior Stroke or transient ischemic attack] ≥2) upon hospital admission. All patients benefited from a comprehensive geriatric assessment. Their risks of stroke and bleeding were predicted using CHADS₂ and HEMORR2HAGES (Hepatic or renal disease, Ethanol abuse, Malignancy, Older (age >75 years), Reduced platelet count or function, Rebleed risk, Hypertension (uncontrolled), Anemia, Genetic factors, Excessive fall risk, and Stroke) scores, respectively.

RESULTS

Anticoagulation underuse was observed in 384 (50%) of 773 geriatric patients with AF (median age 85 years; female 57%, cognitive disorder 33%, nursing home 20%). No geriatric characteristic was found to be associated with anticoagulation underuse. Conversely, anticoagulation underuse was markedly increased in the patients treated with aspirin (odds ratio [OR] [95% confidence interval]: 5.3 [3.8; 7.5]). Other independent predictors of anticoagulation underuse were ethanol abuse (OR: 4.0 [1.4; 13.3]) and age ≥90 years (OR: 2.0 [1.2; 3.4]). Anticoagulation underuse was not inferior in patients with a lower bleeding risk and/or a higher stroke risk and underuse was surprisingly not inferior either in the AF patients who had previously had a stroke.

CONCLUSION

Half of this geriatric population did not receive any anticoagulation despite a clear indication, regardless of their individual bleeding or stroke risks. Aspirin use is the main characteristic associated with anticoagulation underuse.